When picking out cylinder heads to upgrade an engine, in general most people think in terms of flow. However there are many more considerations to be made about such a big decision that can make or “brake” a good engine build. To demonstrate the importance of choosing the right cylinder heads, Richard Holdener teamed up with Comp Cams and RHS to set up a test using a Chevy Small Block that has a reputation for using a poor head casting. Even though the upgrade test conducted does include a camshaft and intake upgrade as well, the main focus is the role a good set of heads plays in making real power.
Richard first installed a 350ci SBC on the Dyno. This particular small block is an L82, the performance 350 offered in the Corvette from 1973-1982, prior to the introduction of Chevys fuel injection engines. It featured a 9.0:1 compression ratio, cast iron 882 heads, and a Quadrajet induction system. It also offered a healthy at the time camshaft with a .450/.460 Lift and 222 degrees of duration. Run on the Dyno in the stock configuration with long tube headers it produced 313 HP @ 5,400 RPM and 355 Lb-Ft of torque @ 3,800 RPM.
With a baseline established it was time for the upgrades. The team removed the L82 cam, heads, and intake to make way for the the Comp XE274H camshaft with .490 lift, 230/236 duration, and a 110 LSA, RHS aluminum heads, and a dual plane high rise intake manifold.
The engines next run on the Dyno proved the teams efforts to be fruitful, with 414 HP and 415 Lb-Ft of torque. The upgrades not only dramatically increased the SBCs peak power but also the power output throughout the entire power band as well.
Focusing on the impact made by the choice of the right heads, Richard explains the considerations made, on top of flow numbers, in the planning stages of the build. The RHS heads not only offered more flow but also smaller combustion chambers. Smaller chambers equals higher compression which equates to more power. In addition, because of the aluminum construction, the RHS heads are lighter weight and have a reduced chance of detonation. All aspects considered, these heads are a win, win, win.